Pursuant to 35 USC xc2xa7119, this application claims the benefit of Japan Patent Application No. 2001-313172, filed Oct. 10, 2001.
The present invention relates to a lens array for unity magnification imaging, particularly to a lens array for unity magnification imaging used preferably in an image reading apparatus mounted on portable electronic apparatuses such as a cellular phone.
In apparatuses such as a facsimile apparatus, copying machine, and scanner, image reading apparatuses such as a contact type image sensor for reading an image on an original copy have heretofore been used. The contact type image sensor has broadly been used because the sensor can be miniaturized.
The contact type image sensor includes: a light source such as an LED array for irradiating the original copy with an illuminating light; a lens array for forming light reflected from the original copy into an image; and a photoconductive device disposed in an image formation point. As shown in FIG. 1, a conventional lens array for unity magnification imaging array 11 of the contact type image sensor forms the image on the original copy as an erected image having a unity magnification on the photoconductive device. The lens array 11 has, for example, a conjugate length TC of about 10 mm, and includes a plurality of rod lenses 12 arranged in two rows.
However, when the contact type image sensor including the conventional lens array 11 is mounted on portable electronic apparatuses such as a cellular phone and personal computer, there has been a problem of increase of a size of the apparatus. Reasons for this are as follows.
(1) An effective image reading width Wi (see FIG. 2) of the rod lens array 11 is smaller than a total width Wt (see FIG. 1) of the rod lens array 11 by 5 to 6 mm. Therefore, it is necessary to secure a space broader than the width essentially necessary for the reading in the apparatus. Here, the effective image reading width Wi in a range in which a constant light amount is obtained (a range from which periodic light amount unevenness is removed). Moreover, Wl in FIGS. 1 and 2 is an effective lens width.
(2) The conjugate length TC of about 10 mm is relatively long, and it is therefore difficult to contain the contact type image sensor including the rod lens array 11 in the portable electronic apparatus which has the existing thickness.
An object of the present invention is to provide a miniaturized lens array.
In a first embodiment of the present invention, a lens array for unity magnification imaging is provided that includes a plurality of rod lenses arranged in at least one row at a lens arrangement pitch D. Each rod lens has an angle of aperture xcex8. The lens arrangement pitch D is defined to satisfy the following equation (1):
(2 m+1)xc2x7Dxe2x89xa62.1 mmxe2x80x83xe2x80x83(1),
wherein m is an overlap degree of the plurality of rod lenses. The angle of aperture xcex8 of the rod lens is defined to satisfy the following equation (2):
xcex1D/6xc3x97{nxc2x7cosxe2x88x921(xe2x88x92xcex1/2/m)+(4 m2/xcex12xe2x88x921)1/2 }xe2x89xa6xcex8xe2x89xa6xcex1D/2xc3x97(4 m2/xcex12xe2x88x921)1/2xe2x80x83xe2x80x83(2),
wherein n is a refractive index on an optical axis of the rod lens, d is an effective diameter of the rod lens, xcex1 is a filling factor of the lens array. The overlap degree m is set in a range of 1.53 to 3.00 when the plurality of rod lenses are arranged in odd-numbered rows. The overlap degree is set in a range of 1.10 to 3.00 when the plurality of rod lenses are arranged in even-numbered rows.
In a second embodiment of the present invention, a lens array for unity magnification imaging is provided that includes a plurality of rod lenses arranged in at least one row at a lens arrangement pitch D. Each rod lens has an angle of aperture xcex8. The lens arrangement pitch D is defined to satisfy the following equation (1):
(2 m+1)xc2x7Dxe2x89xa62.5 mmxe2x80x83xe2x80x83(1),
wherein m is an overlap degree of the plurality of rod lenses. The angle of aperture xcex8 of the rod lens is defined to satisfy the following equation (2):
xcex1D/6xc3x97{nxc2x7cosxe2x88x921(xe2x88x92xcex1/2/m)+(4 m2/xcex12xe2x88x921)1/2 }xe2x89xa6xcex8xe2x89xa6xcex1D/2xc3x97(4 m2/xcex12xe2x88x921)1/2xe2x80x83xe2x80x83(2),
wherein n is a refractive index on an optical axis of the rod lens, d is an effective diameter of the rod lens, xcex1 is a filling factor of the lens array. The overlap degree m is set in a range of 1.53 to 3.00 when the plurality of rod lenses are arranged in odd-numbered rows. The overlap degree is set in a range of 1.10 to 3.00 when the plurality of rod lenses are arranged in even-numbered rows.
In a third embodiment of the present invention, an image reading apparatus is provided that includes a light source for irradiating an original copy with illuminating light, a lens array for unity magnification imaging, for forming the light reflected by the original copy into an image, and a photoelectric conversion unit disposed in an image formation point of the lens array. The lens array for unity magnification imaging includes a plurality of rod lenses arranged in at least one row at a lens arrangement pitch D. Each rod lens has an angle of aperture xcex8. The lens arrangement pitch D is defined to satisfy the following equation (1):
(2 m+1)xc2x7Dxe2x89xa62.1 mmxe2x80x83xe2x80x83(1),
wherein m is an overlap degree of the plurality of rod lenses. The angle of aperture xcex8 of the rod lens is defined to satisfy the following equation (2):
xcex1D/6xc3x97{nxc2x7cosxe2x88x921(xe2x88x92xcex1/2/m)+(4 m2/xcex12xe2x88x921)1/2 }xe2x89xa6xcex823 xcex1D/2xc3x97(4 m2/xcex12xe2x88x921)1/2xe2x80x83xe2x80x83(2),
wherein n is a refractive index on an optical axis of the rod lens, d is an effective diameter of the rod lens, xcex1 is a filling factor of the lens array. The overlap degree m is set in a range of 1.53 to 3.00 when the plurality of rod lenses are arranged in odd-numbered rows. The overlap degree is set in a range of 1.10 to 3.00 when the plurality of rod lenses are arranged in even-numbered rows.
In a fourth embodiment of the present invention, an image reading apparatus is provided that includes a light source for irradiating an original copy with illuminating light, d lens array for unity magnification imaging, for forming the light reflected by the original copy into an image, and a photoelectric conversion unit disposed in an image formation point of the lens array. The lens array for unity magnification imaging includes a plurality of rod lenses arranged in at least one row at a lens arrangement pitch D. Each rod lens has an angle of aperture xcex8. The lens arrangement pitch D is defined to satisfy the following equation (1):
(2 m+1)xc2x7Dxe2x89xa62.5 mmxe2x80x83xe2x80x83(1),
wherein m is an overlap degree of the plurality of rod lenses. The angle of aperture xcex8 of the rod lens is defined to satisfy the following equation (2):
xcex1D/6xc3x97{nxc2x7cosxe2x88x921(xe2x88x92xcex1/2/m)+(4 m2/xcex12xe2x88x921)1/2 }xe2x89xa6xcex823 xcex1D/2xc3x97(4 m2/xcex12xe2x88x921)1/2xe2x80x83xe2x80x83(2),
wherein n is a refractive index on an optical axis of the rod lens, d is an effective diameter of the rod lens, xcex1 is a filling factor of the lens array. The overlap degree m is set in a range of 1.53 to 3.00 when the plurality of rod lenses are arranged in odd-numbered rows. The overlap degree is set in a range of 1.10 to 3.00 when the plurality of rod lenses are arranged in even-numbered rows.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.